New alarming symptoms

I have been diagnosed with Fibromyalgia for over 20 years now. My main symptoms were fatigue and minor pain in muscles.
Three years ago I began experiencing severe dizziness and syncope (fainting). No one can figure out why or ever connected it to my Fibromyalgia. In the last year, I have lost over 20% of my body weight (mostly muscle mass in my legs and arms) and for the last three months I’ve been experiencing extreme pain in all my muscles They have tested me for everything related to inflammatory and autoimmune diseases and even did a MRI of my brain. All of it came back negative.
Could this all be the Fibromyalgia? Has anyone else experienced these symptoms?
I would appreciate any and all advice, experience and opinions.
Thanks